tests: gpiomon: tweak the timing for single event type tests
tests: gpiomon: tweak the timing for single event type tests

Since switching to using libgpiomockup there are some timing problems
with two gpiomon test cases. I'm not sure what the reason is and we'll
be switching to glib unit tests soon, so let's not waste time on that
and just increase the sleep time.

Signed-off-by: Bartosz Golaszewski <e5d45fddd9040473413b909b802f629a971ad04c@baylibre.com>

brgl/libgpiod,brgl/libgpiod,brgl/libgpiod,brgl/libgpiod